A study in the US has found that smoking increases the risk of breast cancer in older women by almost 20%.
The study adds to a growing weight of evidence linking exposure to tobacco smoke and deadly disease.
A representative from a smokers' group has said the law should not be used to "stigmatise smokers as potentially unfit parents" after MPs approved plans to ban smoking in cars carrying children.
Simon Clark, director of the smokers' group Forest, said he was "disappointed but not surprised" by the result and warned that the Government will ban smoking in the home next:
Legislation will have very little impact because so few adults still smoke in cars carrying children. Those that do will carry on because it will be very difficult to enforce.
The overwhelming majority of adult smokers know how to behave towards children and the law should reflect that.
It shouldn't be used to stigmatise them as potentially unfit parents who can't be trusted to do the right thing without state intervention.
If you believed everything you heard in the House about the threat to children's health it's a miracle anyone who was a child in the fifties and sixties, when a large majority of adults smoked, is still alive.
Government has banned smoking in public places. Now they're going to ban it in a private place. The home will be next.
Shadow public health minister Luciana Berger has welcomed the result of a vote to ban smoking in cars with children as a "great victory for child health", but warned ministers not to "kick this into into the long grass".
"This is a great victory for child health which will benefit hundreds of thousands of young people across our country. It is a matter of child protection, not adult choice," the MP said.
"A time-limited consultation may be necessary on the practical details of implementation, but we will be watching closely to ensure the Government don't try and kick this into the long grass."
Some MPs have questioned how the plans will be enforced with some criticising the plans as a "nanny state" ban.
MPs have raised questions as to how the ban on smoking in cars carrying children will be enforced, with some criticising the plans as a "nanny state" ban.
The Health Secretary will be given the power to impose a ban despite the opposition.
Smoking in cars is wrong, but a statutory ban? Who'll enforce it? Do we ban kids standing by fires next! I'm voting against it.
I voted No to the Ban. I totally support the principle but think it will be unenforceable. Education needed.
After much deliberation, I voted against nanny state ban on smoking in cars, I was in a minority, legislation is going to be interesting
Medical charities have said they are "delighted" that MPs voted to approve plans to ban smoking in cars carrying children.
The British Lung Foundation estimate that more than 430,000 children aged between 11 and 15 are exposed to second-hand smoke in cars every week.
"Having campaigned on this issue for many years, we're absolutely delighted that MPs have backed the ban on smoking in cars carrying children," Dr Penny Woods, the charity's chief executive said.
"This could prove a great leap forward for the health of our nation's children.The introduction of a law that would help prevent hundreds of thousands of children from being exposed to second-hand smoke in the car is now within reach.
MPs have hailed plans to ban smoking in cars carrying children after it was overwhelmingly voted through in the Commons.
Despite opposition from some Conservative MPs, including Cabinet members, MPs approved the ban by 376 votes to 107.
Massive victory on banning smoking in cars with children! Brilliant news for children's health!
376-107 to ban smoking in cars with children present....majority 169. Hurrah. Thanks it will make a difference to 500000 children.
MPs have voted overwhelmingly in favour of plans to ban smoking in cars carrying children by 376 votes to 107, a majority of 269.
Shadow public health minister Luciana Berger has said those opposed to a ban on smoking in cars carrying children are the same people who railed against the introduction of laws enforcing seatbelt use throughout the 1970s and 1980s.
The Labour MP, who is urging her Commons colleagues to vote in favour of the ban, said health figures suggest around half a million children are exposed to second hand smoke in the back of the car on a weekly basis.
Critics of the anti-smoking legislation, though, have said such a ban cannot be implemented or will be ineffective - a similar argument, Ms Berger said, that was used to oppose seatbelt laws.
She admitted that "we don't have the exact specifics about how it will work in practice", but said MPs will look to "states in the US," plus "Canada, Australia and South Africa", to see how their equivalent laws are targeting offenders.
MPs have been tweeting their intentions ahead of today's vote in the House of Commons on a legal ban on people smoking in cars carrying children.
I will be voting later today for smoking ban in cars to protect children
My libertarian instincts are wrestling with my profound belief that public health is one of biggest issues facing population #smokingban
Support a ban on smoking in cars and other vehicles - to protect the health of children and others.
The Commons is expected to vote in favour of the ban, though Prime Minister David Cameron - who has declined to share his view on the issue - is set to miss the vote as he remains involved in the Government's response to the floods crisis in the South West of England.
Boris Johnson has used his column in the Daily Telegraph to appeal to party colleagues to accept the "bossyboots brigade" he so often rails against are right in the case of a smoking ban in cars where children are present.
"Surely to goodness - you might say - people these days are aware of the problem of passive smoking? Surely all smokers know that they shouldn't be puffing away in a car, while the pink defenceless lungs of kids are sucking in the evil vapours?" he wrote.
"Alas, I am afraid that people either don't know, or don't care enough.""These kids cannot protest, and very often the smoker in the vehicle lacks the will to stub it out. "This law would give that smoker that extra legal imperative to obey their conscience and do the right thing."
Rejecting critics' claims that it would divert police resources from more serious crimes, he said it would be "largely enforced by the natural social pressure of disapproval backed by law".